According to characteristics of oil and gas accumulation in small and fat oil reservoir, the authors take Beizhong oil field of Beier depression as an example. The typical examples and reservoir sections are analyzed base on the study of logging curves, results of seismic interpretation, logging interpretation data and dynamic development of test data on oil production of exploration-evaluation wells and development well, combined with faults system split results in Beizhong field. On the basis of sag-wide oil bearing in Nanyi (the first member of Nantun Formation) major reservoir of Beizhong oil field, the factors of forming poor oil areas or water areas are loss of major reservoirs within the target layer by the function of fault, causing water areas formed near the faults; adjustment by later reverse faults, oil from Nanyi Layer adjust to Naner (the second member of Nantun Formation) layer or Dayi (the first member of Damoguaihe Formation) Layer formed secondary reservoirs, and causing poor oil areas formed near the reveres faults within main reservoir; oil dynamics migrations and accumulation during oil development, causing quickly water occurrence in lower positions.
